RuO2 Nanorods for Electrochemical Chlorine Evolution and Simultaneous Removal of Ammonia Nitrogen and COD from Wastewater
This study addresses the removal of ammonia nitrogen (NH4+-N) and chemical oxygen demand (COD) from real coal chemical wastewater via electrochemical chlorine evolution. A nanorod-structured ruthenium dioxide catalyst (N-RuO2) was synthesized by modifying ruthenium trichloride precursor with ammonium chloride. Compared with unmodified RuO2, commercial DSA, and commercial RuO2 (Com-RuO2), N-RuO2 exhibited significantly enhanced electrochemical performance: Faradaic efficiency for chlorine evolution increased by 12.9%, 18.5%, and 25.6%, respectively; accelerated lifetime improved by 1.7, 1.9, and 2.9 times, respectively. In treating real coal chemical wastewater, N-RuO2 reduced NH4+-N to 86.4 mg·L−1 and COD to 72 mg·L−1, with degradation rate constants approximately 2.08 and 1.46 times higher than Com-RuO2, while energy consumption decreased by 17.7 Wh·g−1 and 1.5 Wh·g−1, respectively. Further studies showed that increasing chloride ion concentration enhanced removal rates and reduced energy consumption; higher current density accelerated removal but increased energy use; alkaline conditions favored NH4+-N removal, while neutral conditions favored COD removal. The excellent electrochemical performance of RuO2 nanorods indicates broad application prospects in practical water treatment.